Motor system for controlling pressure



1953 R. R. BLAIR 2,649,560

MOTOR SYSTEM FOR CONTROLLING PRESSURE Filed May l7, 1951 2 Sheets-Sheet1 REVERS'E o I 5 OPE ATE FIG.

uvvavron R. R. BL AIR BY ATTOR/VE Y Aug. 18, 1953 R. R BLAIR MOTORSYSTEM FOR CONTROLLING PRESSURE 2 Sheets-Sheet 2 Filed May 17 1951 LIll/l" II m 6t 9. Q Q Q S Q Q Q Q t 5 I t t 7 mm m NM 8 Q S S 2 3 3INVENT'OR R. R. BLAIR BY ATTORNEY Patented Aug. 18, 1953 MOTOR SYSTEMFOR CONTROLLING PRESSURE Boyer R. Blair, Berkeley Heights, N. J.,assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y.,a corporation of New York Application May 17, 1951, Serial No. 226,895

Claims.

This invention relates to pressure controlling apparatus andparticularly to motor-driven apparatus for accurately controlling thespring defiection of point contact varistors.

In the process of manufacturing point contact varistors, it has beenfound necessary to accurately control the contact area across whichrectification occurs in order to obtain uniform electricalcharacteristics. The point contact wire of the varistor, tungsten forexample, shaped to form a spring, is chosen to be of softer materialthan the semiconductor portion of the varistor, silicon or germanium,for example, so that the point of the contact wire is flattened into an,area which is proportional to the force exerted upon the semiconductorby the springshaped contact wire when deflected.

In accordance with an embodiment of the invention herein shown anddescribed for the purpose of illustration, there are provided amotordriven means for moving the spring-shaped contact wire into contactwith the semiconductor and for further advancing the wire to cause thespring to be compressed and pressure to be applied through the springcontact wire to the semiconductor at the area contact and means forstopping the motor when the contact wire has been in contact with thesemiconductor for a predetermined time interval, thereby producing apredetermined deflection of the spring, 0.002-inch for example. Themotor is caused to rotate by supplying current from analternating-current source to its windings through contacts of anelectromagnetic relay when deenergized. When energized, the relayoperates to disconnect the motor windings from the alternating currentsource and to complete circuits for supplying to the motor windingsdirect current preferably from a condenser which has previously beencharged by rectified current derived from the alternating-currentsource, thereby discharging the condenser through the motor windings andcausing the motor to stop quickly.

For controlling the energization of the relay to stop the motor there isprovided a circuit comprising three grid-controlled space currentdevices the second and third of which are of the gas-filled type. Whenthe contact wire engages the semiconductor of the varistor, current froma direct-current source flows through a circuit completed by thevaristor to cause a direct voltage to be set up and to be impressed uponthe control electrode-cathode circuit of the first space current deviceto increase the space current flowing through its anode-cathode path anda resistor in series, thereby causing an increase of voltage across theresistor. The resistor is connected in the control electrodecathodecircuit of the second space current device to initiate conductiontherein in response to the increase of voltage across the resistor.There is provided a circuit having resistance and capacitance in which adirect voltage is set up in response to space current flowing throughthe anode-cathode path of the second device and a portion at least ofsaid resistance, thereby charging the capacitance. The capacitance isconnected in the control electrode-cathode circuit of the third spacecurrent device. After a period determined by the time constant of theresistance-capacitance circuit which is adjustable, the voltage acrossthe capacitance reaches an amplitude sufiicient to initiate conductionin the third space current device in the space current circuit of whichis conneced the winding of the relay, thereby operating the relay andcausing the motor to stop quickly. There is also provided a clock forindicating the time interval between the time that the point of thecontact wire reaches a surface of the semiconductor and the time thatthe relay operates for stopping the motor.

Fig. 1 of the accompanying drawing is a diagrammatic view of anapparatus for automatically adjusting the contact pressure between thesemiconductor element and the conductor contact element of a varistorwhich embodies the invention;

Fig. 2 is a view in elevation partly in section of a portion of thedriving apparatus of Fig. 1; and

Fig. 3 is an enlarged sectional view of a portion of Fig. 2.

Referring to the drawing, there is shown a varistor comprising ametallic tubular terminal element It enclosing an interfering axiallycoincident metallic pin E2 to one end of which is soldered a small waferit of suitably processed semiconducting material such as crystallinesilicon or germanium. A second metallic tubular terminal element Mencloses a second metallic pin IE to one end of which is soldered a wireI6 of a conducting material softer than the semiconducting element [3,tungsten, for example, shaped to form a spring. The terminal element Infits into an anvil I! of metallic material supported by the frame 21! ofa micrometer and insulated therefrom by a bushing 2!. The two terminalelements It! and M of the varistor are supported in axial coincidence bya case I! of insulating material,. for example, silica filled Bakelite.In manufacturing the varistor, it is desired to drive the pin I5 throughthe tubular element It to advance the conducting contact wire element i5toward the semiconductor element |3 to bring an end portion of element[6 into contact with a surface portion of element l3 and to furtheradvance the element It to compress the spring element by a predeterminedamount to increase the pressure at the contact area. The pointed endportion of the wire element I5 is thus flattened to increase the contactarea to a predetermined size determined by the degree of compression ofthe spring element.

The driving means for the pin I5 and the spring contact element itcomprises a micrometer device 20, shown in Fig. 2, and a motor H! fordriving the plunger 22 of the micrometer device through reduction gearshaving a ratio of 25 to 1, for example, in gear box H5. The terminalelement M of the varistor fits into a recessed portion of a guide member23 for the plunger 22, a pin 24 secured in the plunger 22 passingthrough an aperture in guide member 23 to keep the guide member on theplunger 22 and to permit its movement with respect to the plunger sothat a varistor may be inserted in the device. The plunger 22 has anenlarged end portion 25 secured to a rod 26 and insulated therefrom by abushing member 21. The rod 26 is supported by the micrometer frame 20and is adapted to slide through an opening therein, the rod 26 beingprevented from rotating by a pin 20 in the frame 20 engaging anelongated slot in, the rod 25. A spring 29 is adapted to move the guidemember 23 along the plunger 22 so as to hold the terminal elements i andM in place in the anvil H and the guide 23, respectively. The micrometershaft 90 has a threaded portion in engagement with an internallythreaded portion of the micrometer frame and an annular recessed endportion in engagement with a pin 9| secured in the rod 26. The shaft 90is driven by the motor I8 through the gearing 19.

There is provided a three-position switch 30 having contacts designatedby the numerals l to 8, inclusive, and an electromagnetic relay 3|. Thecircuits of Fig. 1 will first be described assuming the switch 30 to bein the operate position and the relay 3| to be deenergized. For thiscondition contacts 2, 4 and E are closed and the remaining contacts areopen. Closure of switch contact 2 completes a circuit through a contactof relay 3| for supplying current from an alternating-current source 32to one of the windings 33 of motor 13. A circuit is completed from oneside of the alternating-current source 32, through switch contact to oneterminal of a second winding 30 of motor i8 and from its other terminal,through switch contact E5, through a condenser 35, through the armaturesand contacts of relay 3| and through switch contact 2 to the other sideof the alternating-current source 32. Condenser 35 and resistor 37 inseries and condenser 38 and resistor 39 in series are provided forreducing sparking at the contacts, respectively, of relay 3|, theseresistors each having a resistance of 470 ohms and these condensers eachhaving a capacitance of 0.25-microfarad, for example. Condenser 35 mayhave a capacitance of 4 microfarads, for example. Condenser 40 andresistor M in series are provided for reducing sparking across switchcontact and condenser 42 and resistor 03 in series are provided forreducing sparking across switch contacts 2 and 8,

these resistors each having a resistance of 22 ohms and these condenserseach having a capacitance of 0.25-microfarad, for example.

There is provided a rectifier comprising a transformer 44 having aprimary winding connected to the alternating-current source 32, a firstsecondary winding connected to the cathode of a rectifier tube 15 and asecond secondary winding the end terminals of which are connected to theanodes, respectively of the tube 45 and a midterminal of which isconnected to a grounded output terminal of the rectifier. The cathode oftube 45 is connected through resistors 06 and ll in series, havingresistance values of 1500 ohms and 1000 ohms, respectively, to thepositive rectifier output terminal, a cold cathode, gas filled voltageregulator tube 03 being connected across the output terminals tominimize voltage changes across the output terminals. A filteringcondenser 49 of 80 microfarads is provided in a path connecting a commonterminal of resistors 46 and H to ground.

There is provided a circuit for controlling the energization of relay 3|comprising space current devices 55, 52 and 53, device 55 being a vacuumtube triode and devices 52 and 53 being gas filled, grid controlledtubes of the type in which space current conduction continues afterbeing started until the voltage of the space current source is reducedto a low value such as zero. Current is supplied from the positiveoutput terminal of rectifier 45 through the space current path of tube5| and through a resistor 54 of 10,000 ohms to ground. Space current issupplied to tube 52 from the positive output terminal of rectifier 45through switch. contact l, resistor 55 of 500 ohms, the anode-cathodepath of tube 52, relay 56, resistor 51 of 5000 ohms ,and a 2000-ohmrheostat 53 to ground. Space current is supplied to tube 53 from thepositive output terminal of rectifier 05, through switch contactresistor 59 of 1000 ohms, relay 3|, the anode-cathode path of tube 53,resistor 60 of 2000 ohms and a 2000-ohm rheostat 3| to ground, acondenser 62 of 0.01 microfarad being provided in a path connecting acommon terminal of resistor 59 and relay 3| toground. A condenser 08 ofmicrofarads is connected across resistor 60 and rheostat 6| in series.There is connected to the output terminals of rectifier across constantvoltage tube 48 a voltage divider comprising in series a resistor 63 of50,000 ohms and a 2000-ohm rheostat 64 which is shunted by a -microfaradcondenser 65. A resistor 66 of 2.7 megohms is provided in a pathconnecting the control electrode of tube 5| and ground. A normally openmicroswitch 61 is provided in a path connecting a common terminal ofresistor 63 and rheostat 04 to the grid electrode of tube 5|, thisswitch being closed only when the circuit is being adjusted.

When the conducting wire electrode It makes contact with thesemiconductor element IS, the voltage across rheostat 04 is impressedupon a circuit comprising in series a resistor 68 of 1 megohm,conducting element and the semiconductor element 53 of the varistor, andresistor '66, thereby setting up across resistor 56 and impressing uponthe control electrode-cathode circuit of tube 5| a voltage forincreasing the space current flowing in tube 5| and thereby increasingthe voltage across resistor 54. The control electrode of tube 52 isconnected through a resistor 10 of 10,000 ohms to the cathode of tube 5|and through a condenser H of 0.01 microfarad to ground. The increase ofvoltage across resister 54 causes space current conduction to beinitiated in tube 52, thereby increasing the potential of the cathode oftube 52 with respect to ground. Conduction in tube 52 prior to the timethat a circuit is completed through the varistor l3, ['6 is prevented bythe biasing voltage across rheostat 58 to which current is supplied fromrectifier 45 through a resistor 12 of 18,000 ohms. A condenser 13 of 0.2microiarad is connected between the anode of tube 52 and a commonterminal of resistor 12 and rheostat 58. There is provided a clock '14energized by current from alternating-current source 32. The clock isstarted in response to the energization of relay 56 to cause adirect-current clutch in the clock (not shown) to be energized. Withrelay 3| deenergized, a circuit is completed from one side of thealternating-current source through a condenser !5 of 80 microfarads,rectifier element '16, a resistor H of 400 ohms and through switchcontact 2 to the other side of the alternating-current source forcausing condenser 15 to be charged. The clutch of clock 74 is energizedfrom the voltage across condenser 15 in response to the energization ofrelay 56.

There is provided a time constant circuit comprising in series a5-megohm rheostat 18, a 50,000-ohm resistor 19, normally closed switch80, a condenser 8| of 1 microfarad, rheostat 58, resistor 51 and relay56. the control electrode of tube 53' is connected through a resistor 82of 50,000 ohms to a common terminal of resistor '59 and condenser 81.The control electrode-cathode circuit of tube 53 is normally biased toprevent space current conduction therein due to the current suppliedfrom rectifier through a resistor 83 of 3300 ohms, resistor and rheostat5| to set up a biasing voltage across resistor and rheostat 6| inseries. Space current conduction is initiated in tube 53 when thevoltage across condenser 8| reaches a sufficient magnitude. Prior to thetime that space current conduction is initiated in tube 52 and whenswitch 30 is in its normal position, condenser 8! is charged to therelatively low voltage across rheostat 58 through a circuit comprising aresistor 84 of 100 ohms and switch contact 3. When the tube 52 becomesconducting, switch 30 being in the operate position, the resultingvoltage increases across relay 5 6, resistor 51 and rheostat 58, inseries, causes condenser 8! to be charged at a rate determined by theresistance in the charging circuit which may be adjusted by means of therheostat 18, thereby adjusting the delay interval between the time thatconduction is initiated in tube 52 and the time at which the voltageacross condenser 8| reaches a sufficient magnitude to cause spacecurrent conduction to be initiated in tube 53.

When relay 3! is released and switch 30 is in the operate position, acircuit is completed from one side of the alternating-current source,through switch contact 2, through the armatures and contacts of relay3|, through a resistor 85 of 50 ohms, rectifier elements 86 and acondenser 81 of 375 microfarads to cause the condenser to be charged.When the relay 3! is energized in response to conduction being initiatedin tube 53, the circuits for supplying alternating current from source32 to motor windings 33 and 34 are opened, the circuit for chargingcondenser 81 is opened, and circuits are completed for causing condenser81 to discharge through the motor windings 33 and 34 for quicklystopping the rotation of motor l8. The time interval during which themotor 18 rotates subsequent to the time With switch closed,

that contact is established between the elements [3 and I6 of thevaristor can thus be accurately controlled. Moreover, since the motorruns at a substantially constant speed and because of the largereduction ratio between the motor shaft and spring conducting elementIt, the movement of element I6 after it contacts the semiconductor 13can be accurately controlled. Substantially uniform contact pressure andarea are thus obtainable in varistors when assembled in accordance withthe method described. The energization of relay 31 transfers thecharging circuit for condenser 15 from the alternating-current source 32to charged condenser 81. The polarity of the charge on the latter issuch that energy from condenser 81 cannot pass through element I6 tocondenser 15. Condenser 15 is thereby effectively disconnected from acharging source without the use of an additional contact on relay 3|.The clock quickly stops when the energy in condenser 15 is dissipatedthrough the clock clutch mechanism. The clock thus indicates the timeinterval elapsing between the time that contact is made between elements13 and I6 of the varistor and the time that the motor is stopped.

When the switch 30 is in neutra position, the energizing circuit formotor winding 33 is incomplete, switch contact 2 being open. For thiscondition, contact I of switch 30 is open and the direct-current supplycircuit for tubes 52 and 53 is open and the spacecurrent conduction inthese tubes is interrupted. Relays 56 and 31 are thus released. Also forthis condition, switch contact 3 is closed to complete a circuit forreducing the charge on condenser. Bl to a low value.

When the switch 30 is moved from neutral position to the "reverseposition, contact 3 remains closed and contacts 5, I and 8 are closed.An energizing circuit for motor winding 33 is completed through switchcontact 8 and the closure of contacts 5 and 1 causes the completion ofan energizing circuit for motor winding 34. The connections to winding34 are reversed with respect to the connections which are made when theswitch 30 is in the operate position. The motor 18 thus runs in reverseto condition the apparatus to permit the removal of the varistor fromthe apparatus and the insertion of another varistor assembly so that thecontact pressure between its semiconductor element and its conductivecontact element may be adjusted as above described.

The microswitch 61 is closed to simulate the making of contact betweenthe elements of a varistor when adjusting the timing interval betweenthe closing of the switch 61 and the energization of relay 3| to stopthe motor [8. This timing interval may be reduced to a very small valueby opening the switch 80 in case it is desired to complete thedeflection of the spring conductive element [6 by hand for experimentalurposes.

What is claimed is:

1. In combination, a semiconductor element, a conductive element,driving means for bringing said elements into contact and for increasingthe contact pressure, means responsive to the making of said contact forsetting up a Voltage the magnitude of which increases to a predeterminedmagnitude over a predetermined time period starting at the time ofmaking said contact, and. means responsive to said voltage ofpredetermined magnitude for stopping said driving means when saidelements have been in contact for said predetermined period.

2. In combination, a'semiconductor element, a conductive element shapedto form a spring, driving means for advancing at a substantially uniformrate one of said elements toward the other to establish a contactbetween said elements and for compressing the spring-shaped conductiveelement to increase the contact pressure, a condenser, means forcharging said condenser over a time period starting at the time ofestablishment of said contact, and means responsive to a predeterminedcharge on said condenser for stopping said driving means a predeterminedtime period after the initial establishment of said contact.

3. In combination, a semiconductor element, a conductive element shapedto form a spring, driving means coupled to one of said elementscomprising a motor, means for energizing said motor to advance at asubstantally uniform rate one of said elements toward the other toestablish a contact between said elements and to further advance saidone element for compressing the spring-shaped conductive element,thereby increasing the pressure at the contact area and flattening thecontact portion of the conductive element to increase the contact area,electroresponsive means, means responsive to the establishment of saidcontact for initiating the energization of said electroresponsive means,and means responsive to said energization of said electroresponsivemeans for a time period of predetermined length for interrupting saidenergization of the motor and for simultaneously braking the motor whenthe elements have been in contact for a predetermined time interval.

4. In combination, a semiconductor element, a wire conductive element ofa material softer than said semiconductor element shaped to form aspring, driving means comprising a motor cou pled to said conductiveelement, means for supplying alternating current to said motor toadvance said conductive element at a substantially uniform rate to bringan end thereof into contact with a surface portion of said semiconductorelement and to further advance said conductive element for increasingthe contact pressure and for flattening the contact portion of saidconductive element to increase the contact area, a circuit comprising acondenser and resistance in series, means comprising a space-currentdevice for initiating the flow of current in said circuit in response tothe establishment of said contact between said semiconductor and saidconductive elements to charge said condenser, and means comprising asecond space-current device responsive to a predetermined voltage acrosssaid condenser for interrupting the supply of alternating current tosaid motor and for braking said motor to stop it quickly.

5. In combination, a first element, a second element shaped to form aspring, driving means coupled to one of said elements comprising amotor, means for energizing said motor to advance at a substantiallyuniform rate one of said elements toward the other to establish acontact between said elements and to further advance said one elementfor compressing the springshaped second element, thereby increasing thepressure at the contact area, means responsive to the establishment ofsaid contact for setting up a voltage which increases with time over avoltage range including a voltage of predetermined magnitude during atime period commencing with the time of establishment of said contact.and means responsive to said voltage of predetermined magnitude forinterrupting said energization of the motor and for simultaneouslybraking said motor to stop it quickly.

ROYER. R. BLAIR.

References Cited in the file of this patent UNITED STATES PATENTS

